The present invention deletes to a sensor and a method for its manufacture U.S. Pat. No. 5,467,636 describes a known sensor in which a planar sensing element is immobilized in gas-tight fashion, by way of a sealing element, in a passthrough of an exhaust-gas-side lower ceramic shaped element. The exhaust-gas-side ceramic shaped element has on the end surface facing away from the exhaust gas a recess which surrounds the passthrough and into which a glass seal is introduced. A further ceramic shaped element, which is joined via a metal solder join to the housing, sits on the glass seal. The glass seal encloses the sensing element inside the recess, and constitutes a gas-tight join between ceramic shaped element and sensing element at this point.
The sensor according to the present invention has the advantage that a mechanically stable and gas-tight join is possible between the planar sensing element and both ceramic shaped elements.
The hermetic seal of the sensing element thereby achieved is vibration-proof, so that while the sensor is being used in the motor vehicle, the sensing element can be immobilized over the utilization period in a mechanically stable and hermetic fashion. The method according to the present invention makes it possible for gas-tight immobilization of the sensing element to be attained efficiently.
A particularly mechanically stable and gas-tight joining between the sensing element and the ceramic shaped elements is achieved if the glass seal covers the sensing element over as large an area as possible, but does not penetrate appreciably into the front region which is subject to high thermal stress when the sensor is later operated. The arrangement of a powdered additional seal on the measured-gas site in front of the glass seal prevents the molten glass from penetrating, during the melting process, into the front region of the sensing element that is subject to high thermal stress. It is advantageous for the manufacturing process that the two ceramic shaped elements are configured, on the end faces which face toward one another, in the form of a die and punch, and act accordingly on one another. This makes possible compression of the glass seal, and of the powdered additional seal that is optionally used, utilizing the geometry of the ceramic shaped elements. The presence of a gap between die and punch has the advantage that the glass seal can escape into the gap upon compression. This makes it possible to work with a high compressive force. At the same time, it prevents the two end faces of the ceramic shaped elements from striking one another. In addition, a further glass seal can be inserted into the annular gap between the ceramic shaped elements, or an annular metal foil or plate can be set in place, thus resulting in a positive joining between the two ceramic elements.